J/ApJ/905/98ivo://CDS.VizieR/J/ApJ/905/98doi:10.26093/cds/vizier.19050098CDSHo A.Y.Q.Perley D.A.Beniamini P.Cenko S.B.Kulkarni S.R.,Andreoni I.Singer L.P.De K.Kasliwal M.M.Fremling C.Bellm E.C.,Dekany R.Delacroix A.Duev D.A.Goldstein D.A.Golkhou V.Z.,Goobar A.Graham M.J.Hale D.Kupfer T.Laher R.R.Masci F.J.,Miller A.A.Neill J.D.Riddle R.Rusholme B.Shupe D.L.Smith R.,Sollerman J.van Roestel J.2022-08-26T13:23:35Z2022-08-05T08:58:49ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frvisible-astronomyspectroscopyWe present ZTF20aajnksq (AT 2020blt), a fast-fading ({Delta}r=2.3mag in {Delta}t=1.3d) red (g-r~0.6mag) and luminous (M_1626{AA}_=-25.9mag) optical transient at z=2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t_j_=1d (observer frame); (2) a luminous (L_0.3-10KeV_=10^46^erg/s) X-ray counterpart; and (3) luminous (L_10GHz_=4x10^31^erg/s/Hz) radio emission. However, no GRB was detected in the 0.74d between the last ZTF nondetection (r>21.36mag) and the first ZTF detection (r=19.60mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E_{gamma},iso_<7x10^52^erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT2020blt are consistent with a classical (initial Lorentz factor {Gamma}_0_>~100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.2020ApJ...905...98Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/905/98CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/682/1205 : Fast transients in the Fornax cluster (Rau+, 2008)J/ApJ/693/1484 : Early optical afterglow catalog (Cenko+, 2009)J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)J/ApJ/701/824 : Afterglows of short and long-duration GRBs (Nysewander+, 2009)J/ApJ/720/1513 : The afterglows of Swift-era GRBs. I. (Kann+, 2010)J/ApJ/746/156 : Radio afterglow observations of GRBs (Chandra+, 2012)J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)J/ApJ/781/37 : Multi-band photometry of GRB 130427A (Perley+, 2014)J/A+A/593/A68 : PTF12os & iPTF13bvn spectra and light curves (Fremling+, 2016)J/ApJ/833/88 : GRB 160509A VLA monitoring campain results (Laskar+, 2016)J/ApJ/859/134 : A VLA study of high-z GRBs. II. GRB140304A (Laskar+, 2018)J/ApJ/886/152 : ZTF early observations of Type Ia SNe. I. LCs (Yao+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/905/98https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/905/98http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/905/98https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/905/98https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/905/98http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/905/98GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/905/98/fig2Keck/LRIS spectrum of AT2020blt at dt=2.44d (MJD=58878.644055)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[3060.9/10304.1] Observed Wavelength, air, in Angstrom units0.1nmem.wldoubleFlux[-1.9e-17/2.3e-17]? Flux, in erg/s/cm2/AngstromcW.m**-2.nm**-1phot.fluxdoublenullableSky[6.5e-18/7.3e-16] Sky flux, in erg/s/cm2/AngstromcW.m**-2.nm**-1phot.fluxdoublee_Flux[5.2e-19/2.9e-17] Uncertainty in FluxcW.m**-2.nm**-1stat.error;phot.fluxdoubleXpix[172/4093] LRIS CCD X Pixelpos.cartesian.x;instr.detintYpix[69.9/116] LRIS CCD Y Pixelpos.cartesian.y;instr.detfloatResponse[3.3e+14/5.2e+16] Responsephys.transmissiondoubleFlag[0/1] Flagmeta.code.errorfloat